Fix the fid bug (#28)

Author: jdneo

Diff for: lib/core.js

@@ -89,10 +89,8 @@ core.getProblem = function(keyword, cb) {
   this.getProblems(function(e, problems) {
     if (e) return cb(e);
 
-    keyword = Number(keyword) || keyword;
-    const metaFid = file.exist(keyword) ? Number(file.meta(keyword).id) : NaN;
     const problem = problems.find(function(x) {
-      return x.id === keyword || x.id === metaFid || x.fid === keyword || x.name === keyword || x.slug === keyword || x.fid === metaFid;
+      return x.fid + '' === keyword + '' || x.name === keyword || x.slug === keyword;
     });
     if (!problem) return cb('Problem not found!');
     core.next.getProblem(problem, cb);